Process for preparing a polymer product having a 2,5-furandicarboxylate moiety within the polymer backbone to be used in bottle, film or fibre applications

ABSTRACT

A process for preparing a polymer having a 2,5-furandicarboxylate moiety within the polymer backbone, and having a number average molecular weight of at least 25,000, includes a transesterification step, a polycondensation step, a drying and/or crystallizing step, and a step where the polymer is subjected to post condensation conditions, and to a polyester-containing bottle or film or fiber-containing woven or non-woven object made from melt-processing poly(ethylene-2,5-furandicarboxylate), where the poly(ethylene-2,5-furandicarboxylate) is obtainable by the process of the invention.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of International Application No.PCT/NL2012/050738 filed Oct. 24, 2012, which claims the benefit ofNetherlands Application No. 2007650, filed Oct. 25, 2011 and the benefitof U.S. Provisional Application No. 61/550,707, filed Oct. 24, 2011, thecontents of all of which are incorporated by reference herein.

TECHNICAL FIELD

This invention relates to a process for preparing polymers having2,5-furandicarboxylic acid (abbreviated to 2,5-FDCA) moieties and to aprocess for preparing such polymers. In particular, this inventionrelates to polyesters and to a process of preparing them at highmolecular weight without suffering from discoloration which can be usedin bottle, film or fibre applications.

BACKGROUND ART

FDCA (also known as dehydromucic or pyromucic acid), is a naturaldi-acid that is produced in the healthy human body at 3-5 mg quantitiesper day. Routes for its preparation using air oxidation of2,5-disubstituted furans such as 5-hydroxymethylfurfural with catalystscomprising Co, Mn and/or Ce were reported recently in WO2010/132740,WO2011/043660 and WO2011/043661.

In GB 621971 polyesters and polyester-amides are prepared by reactingglycols with dicarboxylic acids of which at least one contains aheterocyclic ring, such as 2,5-FDCA. Under melt polymerizationconditions, using sodium- and magnesium methoxide as a catalyst, FDCAdimethyl ester and 1.6 equivalents of ethylene glycol were reacted in atransesterification step at ambient pressure between 160 and 220° C.,after which the polycondensation was carried out between 190 and 220° C.under 3 mm Hg pressure. The product had a reported melting point of205-210° C. and readily yielded filaments from the melt. No additionalproperties were reported for PEF or other FDCA based polyesters in this1946 document.

In HACHIHAMA, Yoshikazu the syntheses of Polyesters containing a FuranRing are reported. In this paper polyesters are produced by condensationof 2,5-FDCA with various α,ω-glycols. According to this paper, esterinterchange has proved to be the most convenient method for2,5-furandicarboxylic acid polyesters, since the acid is difficult to bepurified. The ester interchange reaction is promoted by the presence ofa catalyst such as litharge, a natural mineral form of lead(II) oxide.The polymers made, however, were brown to greyish white.

The publication describes polyethylene-furandicarboxylate (PEF) with amelting point between 220 and 225° C., obtained using a lead catalyst.Also reported were the tri-, tetra-, penta- and hexamethylene diolpolyester analogues with reported melting ranges of 115 to 120° C., 163to 165° C., 70° C. and 143 to 145° C., respectively. For the ethyleneglycol and 1,4-butanediol polyesters, fibre forming properties werereported. The polymers made were reported to be brown to greyish white.

In MOORE, J. A. polyesters derived from furan and tetrahydrofuran nucleiare described. Polymers were prepared using 2,5-furandicarbonyl chlorideas monomer. As a result, polymers in the form of a white precipitatehaving a very low intrinsic viscosity (and hence low molecular weight)were obtained. In addition, a polymer was prepared from 1,6-hexane dioland dimethyl-2,5-furandicarboxylate, using calcium acetate and antimonyoxide as catalyst. The number average molecular weight was low (lessthan 10,000), whereas the molecular weight distribution was relativelyhigh (2.54 instead of about 2). Moreover, the product was greenish.Again, from this reference it would appear near impossible to producepolymers having a 2,5-furandicarboxylate moiety within the polymerbackbone, at high molecular weight and without coloured impurities,without having to use a precipitation and/or purification step.

In WO 2007/052847 polymers are provided, having a 2,5-furandicarboxylatemoiety within the polymer backbone and having a degree of polymerizationof 185 or more and 600 or less. These polymers are made in a three stepprocess involving the esterification of the 2,5-FDCA with a diol firstusing a tin catalyst and a titanium catalyst, and a second stepinvolving polycondensation through an ester exchange reaction. The firststep is carried out catalytically at a temperature within the preferredrange of 150 to 180° C., whereas the polycondensation step is carriedout under vacuum at a temperature within the preferred range of 180 to230° C. The product is then purified by dissolving the same inhexafluoroisopropanol, reprecipitation and drying, followed by the thirdstep, a solid state polymerization at a temperature in the range of from140 to 180° C. Not disclosed, but found by the current inventors, isthat the intermediate product produced by the process of this referenceis darkly coloured. This is therefore the reason for the purificationstep. This essential purification step, and in particular when usinghexafluoroisopropanol, is a serious drawback of this process, severelylimiting the commercialization thereof. The problem vis-à-vis thisrecent development is to produce polymers having a2,5-furandicarboxylate moiety within the polymer backbone, at highmolecular weight and without coloured impurities, without having to usea purification step. Also polyesters from 1,3-propanediol and1,4-butanediol were reported.

Conditions and reported properties of the 3 steps for the 3 polyestersare summarized in Table 1 below.

TABLE 1 Experimental results from JP2008/291244 conditions conditionsstep 1 conditions step 2 step 3 (Solid Monomer (Esterification)(Polycondensation) Stating) Product properties Ethylene 280° C.; 4 hours280° C.; 6.5 180° C. M_(n) = 23000; glycol hours T_(m) = 170° C.; T_(g)= 85° C.; T_(c) = 156° C.; T_(dec) = 332° C. 1,3- 230° C.; 4 hours 230°C.; 6.5 140° C. M_(n) = 15000; propanediol hours T_(m) = 150° C.; T_(g)= 39° C.; T_(c) = 102° C.; T_(dec) = 335° C. 1,4- 170° C.; 4 hours 180°C.; 6.5 150° C. M_(n) = 60000; butanediol hours T_(m) = 170° C.; T_(g) =31° C.; T_(c) = 90° C.; T_(dec) = 338° C.

In JP2008/291244 a method for producing polyester resin including furanstructure is provided. The method for producing a polyester resinincluding a furan structure comprises performing ester exchange reactionof a furandicarboxylic dialkyl ester component with a diol component,and then performing polycondensation reaction in the presence of atitanium tetrabutoxide/magnesium acetate mixed catalyst system. Themolecular weight of the polyester resin leaves still much to desire, asdoes the polymerization time (7.5 hours) to achieve a reasonably highmolecular weight.

In WO2010/077133 a tin catalyst was used for both thetransesterification step and the polycondensation step. Although colourand Mn were better than any result reported at that time, the colour ofthe resulting resin in not good enough for application in bottles,fibres and films.

From the above references, it is clear that PEF has been known for morethan 70 years and that many different recipes have been used in whichtemperatures, pressures, di-acid/diol stoechiometries, catalysts andprecursors (di-acid or di-ester) have been varied.

DISCLOSURE OF THE INVENTION

The invention thus relates to a process for the production of polymersand copolymers having a 2,5-furandicarboxylate moiety within the polymerbackbone. The (co)polymers so prepared are have a number averagemolecular weight of at least 25,000 (as determined by GPC based onpolystyrene standards), and an absorbance as a 5 mg/mL solution in adichloromethane:hexafluoroisopropanol 8:2 mixture at 400 nm of below0.05. The use of these high molecular weight (co)polymers as well astheir use in the preparation of bottles, fibres or films is believed tobe novel. Thus, the invention also relates to these bottles, fibres andfilms.

MODES FOR CARRYING OUT THE INVENTION

More in detail, the process of the current invention is similar to theprocess for preparing poly(ethylene terephthalate) (PET) but has somecharacterizing distinctions. Thus, whereas PET is typically made withcatalysts such as, manganese, cobalt and germanium, as mentioned above,we found that these catalysts result in a coloured product. Likewise,whereas bright-white PET can be made directly from a diol monomer and adiacid monomer, the current inventors found that the use of 2,5-FDCAinevitably results in a coloured product. Moreover, whereas PET istypically made by esterification at polymerization temperatures of250-280° C. and higher, again the inventors found that the polymersbased on 2,5-FDCA made at such polymerization temperatures were colouredproduct. Coloured in this respect can be determined quantitatively bymeasuring the absorbance at 400 nm of a 5 mg/mL solution of the(co)polymer in dichloromethane:hexafluoroisopropanol 8:2 solventmixture. If the absorbance is 0.05 or greater, then the product isdeemed inferior.

Moreover, the current inventors found that the analogous process resultsin the formation of a by-product with a lower molecular weight, whichtherefore results in a broader molecular weight distribution. Thisadversely affects the properties of the polymers so produced.

These problems have been addressed, as discussed hereinafter.

Thus, the process of the current invention is a three-step process,wherein first a prepolymer is made having a 2,5-furandicarboxylatemoiety within the polymer backbone. This intermediate product ispreferably an ester composed of two diol monomers and one diacidmonomer, wherein at least part of the diacid monomers comprises2,5-FDCA, followed by a melt-polymerization of the prepolymers undersuitable polymerization conditions. Such conditions typically involvereduced pressure to remove the equimolar excess of diol monomers.

A skilled person will realise that the amounts of diester and diol mayvary. Suitably the diol and diester are used in a diol to diester molarratio of 1.5 to 3.0, more preferably 2.0 to 2.5.

For instance, within the scope of the current invention, in step 1,dimethyl-2,5-furandicarboxylate is reacted in a catalysedtransesterification process in the presence of a metal catalyst withabout 2 equivalents of a diol, to generate the prepolymer whilstremoving 2 equivalents of methanol. Dimethyl-2,5-furandicarboxylate ispreferred, as this transesterification step generates methanol, avolatile alcohol that is easy to remove. However, as starting materialdiesters of 2,5-FDCA with other volatile alcohols, diols or phenols(e.g., having a boiling point at atmospheric pressure of less than 150°C. may be used as well. Preferred examples therefore include ethanol,methanol, or a mixture of ethanol and methanol. Alternatively, insteadof starting with dimethyl-2,5-furandicarboxylate, the diester ofethylene glycol, di(hydroxyethyl)-2,5-furandicarboxylate, can be used aswell. In this case the transesterification with ethylene glycol can beskipped.

The inventors have found that it is preferred that in case the dimethylester of FDCA is used, the first step is a transesterification step,catalysed by a specific transesterification catalyst, preferably for aperiod of 1 to 3 hours at preferred temperature range of from about 150to about 220° C., preferably in the range of from about 180 to about200° C. and carried out until the starting ester content is reduced,preferably until it reaches the range of less than 1 mol % to about 0.1mol %. The transesterification should preferably be performed for atleast one, but more preferably for at least 2 hours at a temperatureabove 180° C. Longer reaction times at lower temperature can be used aswell but this is less desired from an economic point of view. Thetransesterification catalyst may be removed or may be neutralized byadding a Lewis base, to avoid interaction in the second step ofpolycondensation, but can be included in the second step.

Examples of alternative or additional transesterification catalysts thatmay be used in step 1 include one or more of titanium(IV) alkoxides ortitanium(IV) chelates, mixtures of salts of calcium or magnesium orstrontium or zinc, or a mixture of any of these salts. In the case ofethylene glycol containing polyesters, one or more of calcium ormagnesium or strontium or zinc salts are particularly suitable. Althoughthese alternative or additional catalysts may be suitable for thetransesterification, they may actually interfere during thepolycondensation step which will require the addition of a Lewis basebefore starting the polycondensation step. Therefore a preferredtransesterification catalyst for the reaction ofdimethyl-2,5-furandicarboxylate with ethylene glycol is a solublecalcium or zinc salt, such as calcium or zinc acetate. In respect of thecatalyst, it should be realized that the active catalyst as presentduring the reaction may be different from the catalyst as added to thereaction mixture. Ligands or counterions will be exchanged in thereactor.

The catalysts are used in an amount of about 0.005 mol % relative toinitial diester to about 0.2 mol % relative to initial diester, morepreferably in an amount of about 0.01 mol % of initial diester to about0.05 mol % of initial diester.

Step 2 of the process of the current invention, is a catalyzedpolycondensation step, wherein the prepolymer is polycondensed underreduced pressure, at an elevated temperature and in the presence of asuitable catalyst.

The intermediate product from step 1 (i.e., the prepolymer) may, butimportantly need not be isolated and/or purified. Preferably, theproduct is used as such in the subsequent polycondensation step. In thiscatalyzed polycondensation step, the prepolymer is polycondensed underreduced pressure, at an elevated temperature and in the presence of asuitable catalyst. The temperature is in the range of about the meltingpoint of the polymer to about 30° C. above this melting point, but notless than 180° C. The pressure should be reduced gradually to as low asit is possible, preferably below 1 mbar.

Again, the inventors have found that it is preferred that this secondstep is catalysed by a specific polycondensation catalyst and that thereaction is carried out at mild melt conditions.

Examples of suitable polycondensation catalysts include titaniumalkoxides or antimony salts such as solubilised antimony oxide orantimony acetate.

The polycondensation catalysts are used in an amount of about 0.005 mol% relative to initial diester to about 0.2 mol % relative to initialdiester, more preferably in an amount of about 0.02 mol % of initialdiester to about 0.16 mol % of initial diester, even more preferablyfrom about 0.04 mol % of initial diester, to about 0.16 mol % of initialdiester.

A preferred polycondensation catalyst is solubilised antimony oxide,e.g., antimony glycolate, which can be obtained after refluxing antimonyoxide over night in ethylene glycol. Another option which is acombination of transesterification catalyst and polycondensationcatalyst that is of particular interest, is based on a tin(IV) typecatalyst during transesterification, which is reduced to a tin(II) typecatalyst during the polycondensation. Reducing compounds to be usedinclude phosphites, such as alkyl and arylphosphites, withtriphenylphosphite and tris(nonylphenyl)phosphite as preferred examples.

Of particular interest is that the combination of tin(IV) type catalystand tin(II) type catalyst retains activity, allowing the same catalystto be used for a subsequent solid state polycondensation as the thirdstep in the polymerization process.

Step 3 is a solid state polycondensation (SSP), which is a commonprocess used in the preparation of PET. In SSP processes pellets,granules, chips or flakes of polymer are subjected for a certain amountof time to elevated temperatures (below melting point) in a hopper, atumbling drier or a vertical tube reactor or the like.

The inventors found that when the preferred catalysts were used forsteps 1 and 2 and when the preferred process conditions were used forsteps 1 and step 2, the desired end-groups may be obtained after thepolycondensation step, allowing to reach a number average molecularweight larger than 25,000 during the solid stating step. These molecularweights are advantageous as they allow the production of bottles viaInjection Stretch Blow Moulding, melt spinning of fibres and extrusionof films with very good mechanical properties. These products obtainedfrom high molecular weight FDCA-based polymers are considered to be new.

In JP2008/291244 Mitsubishi dissolved and precipitated the resin basedon the 2,5-furandicarboxylate moiety, and then solid stated at atemperature of 140 to 180° C. The applicants have found that this is nota reasonable procedure for the production of polyesters useful inordinary commodity applications. The applicants have found that solidstating of the resin is critical and that temperatures of 190° C. orhigher, and preferable 200° C. or higher, are desirable. The upper limitis restricted by the resins tendency to stick to itself as thetemperature approaches the melting point of the resin. Therefore, thetemperature should be raised very slowly in order to get above thedesired 200° C.

Applicants have found the solid stating process to be slow, even atthese relatively elevated temperatures, and it is preferred to use smallpellets. Suitable pellet size, for example, may be about 100 or morepellets per gram, or preferably 200 or more pellets per gram. Evensmaller pellets can be used to advantage, and for example may beproduced using a “micropelletizing” technology such as from GalaIndustries. An alternative technology, using sintered particletechnology, might also be advantageous. In this technology, very smallparticles are physically stuck together into larger, porous pellets inorder to have a short path length for diffusion of vapours but stillretain a larger macro pellet size for conveyance and melting inextrusion devices. An example of such a technology used for PET recycleis applied by Phoenix Technologies International LLC of Ohio, USA.

Polyesters and various copolymers (random or block) may be madeaccording to the process of the current invention, depending on theselection of the monomers used. For instance, linear polyesters may bemade with 2,5-FDCA (in the form of its methyl ester) and an aromatic,aliphatic or cycloaliphatic diol. The 2,5-FDCA ester may be used incombination with one or more other dicarboxylic acid esters or lactones.Likewise, the diol may be a combination of two or more diols. Polyestersthat have never been produced before and that are claimed in thisapplication are those having both a 2,5-furandicarboxylate moiety withinthe polymer backbone, as well as a 1,4-bis(hydroxymethyl)cyclohexane(either of the stereoisomers or a mixture thereof) or1,1,3,3-tetramethylcyclobutanediol (either of the stereoisomers or amixture thereof) or 2,2-dimethyl-1,3-propanediol or poly(ethyleneglycol) or poly(tetrahydofuran) or glycerol or pentaerythritol or lacticacid (derived from L or D lactide or a mixture thereof) or6-hydroxyhexanoic acid (e.g., derived from caprolactone) within thepolymer backbone.

The polymers and copolymers according to the current invention need notbe linear. If a polyfunctional aromatic, aliphatic or cycloaliphaticalcohol is used, or part of the diol is replaced by such a polyol, thena branched or even cross-linked polymer may be obtained. A branched orcross-linked polymer may also be obtained when part of the 2,5-FDCAester is replaced by an ester of a polyacid.

Examples of suitable diol and polyol monomers therefore include ethyleneglycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol,1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,1,4-cyclohexanedimethanol, 1,1,3,3-tetramethylcyclobutanediol,1,4-benzenedimethanol, 2,2-dimethyl-1,3-propanediol, poly(ethyleneglycol), poly(tetrahydofuran), 2,5-di(hydroxymethyl)tetrahydrofuran,isosorbide, glycerol, pentaerythritol, sorbitol, mannitol, erythritol,threitol.

Preferred examples of diols and polyols are ethylene glycol,1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol,1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, poly(ethylene glycol),poly(tetrahydofuran), glycerol, pentaerythritol.

Suitable dicarboxylic acid esters or polycarboxylic acid esters to beused in combination with the 2,5-furandicarboxylate ester thereforeinclude dimethyl terephthalate, dimethyl isophthalate, dimethyl adipate,dimethyl azelate, dimethyl sebacate, dimethyl dodecanedioate, dimethyl1,4-cyclohexane dicarboxylate, dimethyl maleate, dimethyl succinate,trimethyl 1,3,5-benzenetricarboxylate.

Preferred examples of dicarboxylic acid esters or polycarboxylic acidesters to be used in combination with the 2,5-furandicarboxylate esterare dimethyl terephthalate, dimethyl adipate, dimethyl maleate, dimethylsuccinate, trimethyl-1,3,5-benzenetricarboxylate. More preferably, thesemay be present in a molar ratio of about 10:1 to about 1:10 vis-à-visthe 2,5-furandicarboxylate ester. This mixture of reactants is referredto as the acid ester reactant.

Preferred examples of lactones to be used in combination with the2,5-furandicarboxylate ester are pivalolactone, caprolactone andlactides (L,L; D,D; D,L).

The polymers of the current invention are of value in all forms ofapplication where currently PET and similar polyesters are used. Forinstance, they may be used in fibres, films and packaging materials.

The polymers of the current invention may be used as such or in blendsand compounds. They may contain other components such as plasticizers,softeners, dyes, pigments, antioxidants, stabilizers, fillers and thelike.

As can be seen above, although resins based on the2,5-furandicarboxylate moiety have been produced in the past 70 yearsand are described in the literature, very little is known about thephysical properties or the performance of the material when it issubjected industrially relevant processing conditions to obtain bottles,fibres and films. The inventors have discovered and describe herein thatthe processing of these resins into useful products is possible,although the conditions of the processing and the properties of theresin and thus its synthesis needs to be optimized for the desiredprocessing to be successful.

Examples are provided that give details on work which was conductedusing a PEF resin, with direct comparison to a PET resin. As shown inthe example, the PEF resin has a higher softening point, byapproximately 10-12° C. This attribute can be used to benefit when it isdesired, for example, to pasteurize in a bottle or container after ithas been filled, or when it is desired to fill the package with a hotliquid.

Example 4 shows work comparing the stress-strain relationship fordrawing a PEF resin compared to a PET resin, at temperatures above theglass transition temperature of the resin. The PEF resin is stiffer(higher modulus) than the PET resin and also undergoes a more pronouncedyield and a delayed onset of strain hardening. This has significantimplications for the production of useful materials and packaging fromthe PEF resin.

Example 5 describes the production of injection stretch blow mouldedbottles from PEF. The material distribution in these first bottles wasnot as uniform as desired, and the inventors believe that this is atleast in part due to the late onset of strain hardening. Even so, thematerials were tested and found to have superior barrier properties foroxygen, CO₂, and water, when compared to PET bottles made using the samemould.

Prior to the present invention, the high barrier properties of PEF in anoriented structure, such as a bottle, were unknown. The use of PEF for apackaging material on the basis of these barrier properties is new. Thebarrier properties are such that a carbonated soft drink container couldbe made smaller than current containers and still have a useful shelflife, because the rate of passage of CO₂ gas through the container willbe reduced. Current products are limited either by absolute loss ofcarbon dioxide pressure or by the changing pressure of carbon dioxideand the resultant change in properties.

The use of PEF for packaging of oxygen sensitive materials is also new.The barrier properties of the PEF bottle are such that the rate ofpenetration of oxygen into the container is reduced by five-foldcompared to a conventional PET container. This level of oxygen barriermay be sufficient to use the resin for packaging of oxygen sensitivematerials such as fruit juices, vitamin waters, beer, and wine withoutrelying on costly oxygen scavengers or multilayer film technology. Ifoxygen scavengers are still used, in order to further increase the shelflife, for example, then the quantity of oxygen scavenger can be reducedrelative to the amount which is needed in a conventional PET bottle.

When PEF or other resins based on the bio-derived 2,5-furandicarboxylatemoiety are used for packaging, such as bottles, then it may also bedesired to incorporate other improvements into the packaging, such asuse of a bio-based closure. Exemplary materials for closures include theuse of poly(hydroxyl butyrate-co-valerate) (PHBV), otherpoly(hydroxyalkanoates), poly(lactic acid), or new bio-based materialssuch as poly(butylene succinate). The label may be of a clear orcoloured material, and may be attached with adhesives or used as ashrink sleeve. Either the adhesive or the shrink sleeve could be made,for example, from bio-based materials including but not limited topoly(lactic acid) based materials. It may also be desirable to include adye in the resin formulation in order to give a distinctive look to thepackaging or to protect the materials inside from light. For example, adark amber or green bottle might be suitable for the packaging of beer.For “clear” bottles a suitable amount of a bluing agent can be used tohelp mask the small amount of yellow colour which is found in manypolymeric resins, including those based on the 2,5-furandicarboxylatemoiety. If it is desired to print directly unto the resin based on the2,5-furandicarboxylate moiety then various surface treatments, such ascorona treatment, may be useful for modifying the nature of the printadsorption. If used as a packaging material then the resin may also besubjected to sterilization using any of the techniques known in the art,including but not limited to ozone treatment, UV treatment, e-beamtreatment, and the like.

On the basis of the stress-strain findings detailed in the example, theinventors believe that the optimum properties for a bottle, for example,will rely on having higher stretch ratios than a conventional PET bottledesign. The inventors believe that the optimum axial stretch ratio maybe in the range of 2.0 to 4.0, and more preferably in the range of 2.6to 3.7. Optimum radial ratios may be in the range of 5 to 7.0, and morepreferably in the range of 5.3 to 6.8. The overall areal ratio willpreferably be in the range of 16 to 25, and more preferably in the rangeof 18 to 23.

Preferred bottle sizes for the stretch ratios described above will be inthe range of 300 ml to 2 liter.

The inventors believe that the bottle sidewall thickness might suitablybe in the range of 0.005 inch to 0.015 inch (0.13-0.38 mm), and morepreferably in the range of 0.007 to 0.010 inch (0.18-0.25 mm). Thecombination of high tensile modulus and high barrier properties allowfunctional products to be made even when using a reduced amount of resinon a volume basis, compared to conventional PET resins. The high modulusmay also translate into stiffer bottles with less pronounced creep,further improving the package stability. The tensile modulus of PET barswas found to be approximately 340,000 psi (23.4 kbar) at roomtemperature, whereas the tensile modulus of PEF bars was found to be590,000 psi (40.7 kbar).

The optimal resin molecular weight for suitable bottle production viainjection stretch blow moulding processes is not yet completelyunderstood, but the inventors believe that the number average molecularweight of the resin should preferably be in the range of 25,000 to50,000, and more preferably in the range of 31,000 to 47,000, and mostpreferably in the range of 35,000 to 44,000. The number averagemolecular weight is determined by gel permeation chromatography (GPC)using polystyrene standards. The applicants believe that use of a highermolecular weight resin will help to overcome the delayed onset of strainhardening.

As with other polyesters, it is desirable to crystallize the polymerpellet to prevent sticking and to enable high temperature drying toeliminate degradation due to hydrolysis in the processing equipment.Drying can be conducted at any convenient temperature below the meltingpoint of the polymer. It is essential that the polymer used for criticalapplications such as bottle manufacture be thoroughly dried beforeprocessing in order to maintain a consistent molecular weight.Preferably the moisture content will be less than 200 ppm by weight, andmore preferably less than 50 ppm by weight.

As an alternative to a high number average molecular weight, it is alsobe possible to modify the resin by incorporating a high molecular weightcomponent. The high molecular weight component can be either based onthe 2,5-furandicarboxylate moiety or based on an entirely differentresin. If it is based on the 2,5-furandicarboxylate moiety then a highmolecular weight material can be produced by the use of coupling agentsor branching agents, as are known in the art and which are available forreactions of the hydroxyl terminal groups or of the acid terminalgroups. For the methods of production described herein, the predominantterminal group is believed to be hydroxyl. Suitable coupling agentsinclude, but are not limited to, materials such as triphenyl phosphiteor other multi-site phosphites, pyromellitic anhydride or othermultifunctional anhydrides, isocyanates, multifunctional epoxides,multifunctional carbodiimides, and so forth.

Applicants have found that it was possible to heat the preforms to thedesired temperature for blowing without the use of any reheat additives.However, it may well be desirable to include reheat additives tooptimize cycle times and power absorption into the preforms. Suitablematerials are known in the art.

One very relevant finding is that the resins based on the2,5-furandicarboxylate moiety are very slow to thermally crystallize. Inpractice this means that it is not necessary to reduce the rate ofthermal crystallization in resins used for bottle production. Mostpoly(ethylene terephthalate) bottle grade resins include a small amount,on the order of 1-5 mol % of a diacid such as isophthalic acid in orderto retard the crystallization. Applicants have discovered that no suchcrystallinity disrupter is need for resins based the2,5-furandicarboxylate moiety. The preferred bottle resin is believed tobe a resin based on the 2,5-furandicarboxylate moiety which containsless than 2 mol % of any other diacid, more preferably less than 1 mol %of any other diacid, and most preferably less than 0.3 mol % of anyother diacid. This is in contrast to PET polymer resins used forbottles.

The process of polymer production invariably leads to a small amount ofdiethylene glycol being produced. Applicants have found, that similar toPET production, it is desirable to minimize the amount of this materialwhich is formed. The preferred PEF resin has less than 2 mol % ofdiethylene glycol and more preferably less than 1 mol % diethyleneglycol, and most preferably less than 0.7 mol % of diethylene glycol.

Resins suitable for the use in bottles will preferably not containsignificant levels of acetaldehyde, which can impart off-flavors to thebeverage. It is an important function of solid stating the resin toallow the any acetaldehyde which is present to diffuse out of thepellets. It is also important that in subsequent melt-processing stepsthose conditions be selected so as to minimize the formation of any newquantities of acetaldehyde. The applicants have found that it ispossible to melt-process a PEF resin at temperatures below 250 C andproduce a useful material. For example, in the production of preformsfor injection stretch blow moulded bottles, it is typical to process PETat temperatures of 260° C. or higher, and often 265° C. or higher. ForPEF we have found that it is possible, and preferable, to process at atemperature of less than 250° C. and more preferably less than 240° C.It is preferred that a temperature range of 230° C. to 240° C., as itwill give the most desirable results for the barrel temperature duringinjection moulding of PEF preforms.

The PEF resin has a higher modulus and a higher glass transitiontemperature than PET resin, and so will require somewhat highertemperatures for bottle blowing. Applicants believe that the optimumtemperature for injection stretch blow moullding of bottles will be inthe range of 98° C. to 112° C., and more preferably in the range 102° C.to 108° C. Bottle machine parameters such as timing of the variousevents, injection rod speed, inflation pressure, inflation time, mouldtemperature, and so forth are all parameters which can be adjusted toinfluence the bottle blowing process. It is anticipated that use of aheat set step may also be useful to further enhance the temperaturestability of the bottle.

Specifics in the preform design can also be used to modify the bottlecharacteristics and help to smooth out the material distribution.

The following examples illustrate the current invention.

EXAMPLES

Materials

2,5-Furandicarboxylic acid (FDCA) and dimethyl-2,5-furandicarboxylate(DMF) were prepared according to WO2011043660. Diols, solvents andcatalysts were supplied by Aldrich and used as received.

Analytical Techniques

GPC measurements were performed on a Merck-Hitachi LaChrom HPLC systemequipped with two PLgel 10 μm MIXED-C (300×7.5 mm) columns.Chloroform:2-chlorophenol 6:4 solvent mixture was used as eluent.Calculation of the molecular weight was based on polystyrene standardsand carried out by Cirrus™ PL DataStream software.

UV-visible spectra and absorbances were recorded on a Heliosa(ThermoSpectronic) spectrophotometer.

Example 1 Polymerization with Ca—Sb Catalyst System

Polymerizations were carried out in a 15 liter stirred batch reactor.Dimethyl 2,5-furandicarboxylate (5.0 kg; 27.17 mol), bioethylene glycol(4.02 kg; 64.83 mol) and Ca acetate monohydrate (8.48 g (48.1 mmol) weremixed under nitrogen in the pre-dried reactor, while heating to atemperature of 130° C. when the methanol starts to distill off. Thetemperature is kept at about 130° C. till most of the methanol isdistilled out. Subsequently, the temperature is raised to 190° C.(mantle temperature) under nitrogen flush for 2 hours. Then Sb glycolate(3.48 g Sb₂O₃ dissolved in 200 mL bioethylene glycol) was added understirring at 40 rpm. The temperature was increased to 210° C. whilevacuum was applied slowly. At 300 mbar most of the ethylene glycol wasdistilled off. Finally, the vacuum was reduced as much as possible, butdefinitely below 1 mbar. The mantle temperature was raised to 240° C.and the molecular weight increase was monitored by measuring the stirrertorque.

The polymer that was obtained from the reactor was shown to have a Mn of16.000 g/mol and a Mw/Mn of 2.5. Solid state polymerization experimentswere performed in a tumble dryer. During the first 12 hours,crystallization of the polymer was performed at 145° C. Subsequently,during a period of 72 hours, the temperature was slowly raised to above200° C. Care was taken that polymer particles do not stick together.After 72 hours, the polymer had a M_(n) of 30000 and M_(w)/M_(n) of 2.1

Example 2 Polymerization with Zn—Sb Catalyst System

Transesterification

Into a 100 mL three-necked flask equipped with nitrogen inlet,mechanical stirrer and condenser set into horizontal position, 13.8 gDMF, 11.1 g ethylene glycol and 150 μL Zn(II) acetate stock solution(c=25.5 mg/mL) in ethylene glycol were added. Slow nitrogen flow wasapplied and then the flask was immersed into a 220° C. oil bath.Methanol started to distil at 137° C. After methanol distillation hassubsided (˜20 minutes), the condenser was set to a vertical position toreflux ethylene glycol. Nitrogen gas was continuously flowing through.Transesterification was finished after 4 hours, when 200 μL triethylphosphonoacetate stock solution (c=46.7 mg/mL) was added (1.5:1.0 molarratio of phosphonoacetate:Zn). After 5 minutes stirring, 236 μL antimonystock solution (c=13.9 mg/mL Sb₂O₃) was measured and added to themixture which was stirred for another 5 minutes. The ¹H NMR spectrum ofa sample taken after 4 hours showed less than 0.04 mol % (relative tofuran ring) methyl ester end group.

Polycondensation

After completion of catalyst addition, vacuum was slowly applied and thetemperature was raised to 240° C. (oil bath temperature). The stirrerspeed was set to 100 rpm. After 3 hours polycondensation the vacuum wasreleased and the PEF was taken out by a spoon. M_(n)=17900; M_(w)=42800;PDI=2.39; A(30 mg/mL)=0.007 (measured indichloromethane:hexafluoroisopropanol 8:2 at 400 nm)

Solid State Polymerization (SSP)

SSP experiments were carried out in small glass tubes (17 cm high, 8 mminner diameter) closed with glass frit (P1) on one end and placed in analuminum block heater equipped with nitrogen inlet. The polymer wasground and sieved into 0.6-1.4 mm particles then crystallized at 110° C.overnight. After crystallization, 100 mg polymer was measured into eachtube. SSP was conducted at 210° C. under a nitrogen flow of 4.0 mL/min.After two days SSP (Table 2), as high as 52000 M_(n) was achieved.

TABLE 2 SSP results of PEF prepared with Zn—Sb catalyst system. SSP TimeMn Mw PDI 0 day 17900 42800 2.39 1 day 45500 112400 2.47 2 days 52200126900 2.43 5 days 48200 124700 2.58

Example 3

A sample of PEF resin, with molecular weight approximately 30,000 Mn,was made into a straight sided bar sample using an injection mouldingmachine. A sample of PET resin, Eastar EN052 PET, was also moulded usingthe same equipment. The bars were subjected to a heat distortionmeasurement according to ASTM E2092. The heat distortion temperature ofthe PET sample was found to be 64.5° C. and the heat distortiontemperature of the PEF sample was found to be 76.6° C., or 12° C. higherthan the heat distortion temperature of the PET reference bar. Figure 1shows the test results.

Example 4 Stress Strain Curves for PEF and PET Above Tg

Sample films were prepared from a PET resin and from a PEF resin, andsubjected to tensile testing using a TA Instruments ARES instrument. Theresulting stress-strain curves are shown in Figures 2 and 3. The PEFfilms show a very pronounced yield, with strain hardening at highextensions. The onset of strain hardening at 90° C. was approximately 3×extension, and at 95° C. it was at 4×. The PET films show a lesspronounced yield and earlier onset of strain hardening. For PET theonset at 90° C. was approximately 2.5× extension and at 95° C. it wasjust over 4×. For PET the yield stress was approximately 2-3*10⁶ Pa,whereas for PEF it was 6-18*10 Pa at the same temperatures. Typicallythe PEF will need to be processed (for blow moulding step) at somewhathigher temperature than PET, in order to reduce the modulus so thatinflation can occur. In that case, for example at 100° C., the onset ofstrain hardening was at about 5× for PEF with a yield stress of 3*10⁶Pa. This compares to PET at 90° C., where the yield stress was similar,but the onset of strain hardening was at 2.5×.

Example 5 Bottle Blowing Using PEF Resin

PEF resin with a number average molecular weight of approximately 29,900was crystallized and dried. Several kilograms were used in an Arburg 320M injection moulding machine to injection mould a preform of 26.4 gramweight. The same preform, when used with PET resin, yields a preform of24.5 gram weight. The PEF preforms were produced using an injectionmoulding barrel temperature of 235 C, whereas the PET was produced usinga temperature of 268° C. The overall cycle time for the PEF injectionmoulding was faster than the PET injection moulding, at 21 seconds and25 seconds, respectively.

The preforms were subsequently blown into bottles using a Sidel SBO1/2blow moulding machine using a 24 ounce straight wall model, suitable forcarbonated soft drink bottles. A large variety of conditions weretested, and eventually a preform temperature of 102° C. was found to bebest for the PEF resin. Material distribution was still less even thandesired, but bottles could be made and tested. The PET was blown intobottles with a preform temperature of 98° C.

Testing of the side panels revealed that the PEF had an oxygen barriermore than five-fold better than the PET bottle panel, and CO₂ wasapproximately two-times better. Testing on the whole package revealedthe water barrier to be about two times better also.

Molecular weight of the resin in the final bottle was determined to beapproximately 27,000 Mn.

REFERENCES

-   [1] Hachihama, Y.; Shono, T.; Hyono, K. Synthesis of Polyesters    containing Furan Ring, Technol. Repts. Osaka Univ. 1958, 8, 475-480.-   [2] Moore, J. A.; Kelly, J. E. Polyesters Derived from Furan and    Tetrahydrofuran Nuclei. Macromolecules, 1978, 11, 568-573.

The invention claimed is:
 1. A process for preparing apoly(ethylene-2,5-furandicarboxylate) polymer having a number averagemolecular weight of at least 25,000, as determined by GPC based onpolystyrene standards, wherein the process comprises: (a) a first stepwhich is providing a molten reaction mixture comprisingbis(2-hydroxyethyl)-2,5-furandicarboxylate; (b) a polycondensation stepat reduced pressure and at elevated temperature, wherein under meltconditions the product provided in step (a) is reacted in the presenceof a polycondensation catalyst and removing the condensate from thereactor; (c) drying and/or crystallizing the obtained condensate at atemperature from 90 to 145° C.; and (d) subjecting the polymer of step(c) to post condensation conditions comprising a elevated temperaturetreatment ending at a temperature of at least 190° C. to thereby obtaina poly(ethylene-2,5-furandicarboxylate) polymer having a number averagemolecular weight of at least 25,000; wherein the temperature isincreased by 5 to 25° C. per hour.
 2. The process according to claim 1,wherein after removal from the reactor the condensate is cooled andshaped into pellets for subsequent solid stating step.
 3. The processaccording to claim 1, wherein the conditions in step (d) furthercomprise providing an inert gas or vacuum.
 4. The process according toclaim 1, wherein the elevated temperature treatment of step (d)comprises a temperature treatment starting at 180° C. until atemperature of at least 205° C.
 5. The process according to claim 1,wherein the number average molecular weight is determined by GPC basedon polystyrene standards.
 6. The process according to claim 1, whereinthe polymer is subjected to strain hardening to improve mechanicalproperties.
 7. The process according to claim 1, wherein the moltenreaction mixture comprises bis(2-hydroxyethyl)-2,5-furandicarboxylateprepared by a transesterification step whereindimethyl-2,5-furandicarboxylate ester (diester) is transesterified withethylene glycol (diol) in the presence of a transesterificationcatalyst.
 8. The process according to claim 7, wherein the diol anddiester are used in a diol to diester molar ratio of 1.5-3.0.
 9. Theprocess according to claim 7, wherein the transesterification isperformed at a temperature from 150 to 230° C.
 10. The process accordingto claim 7, wherein methanol is removed from the transesterificationstep up to a temperature of 230° C.
 11. The process according to claim7, wherein the transesterification catalyst is a calcium or zinccatalyst and the polycondensation catalyst is an antimony catalyst. 12.The process according to claim 1, wherein the reduced pressure in step(b) is below 1 mbar.
 13. The process according to claim 1, wherein theelevated temperature in step (b) is below 240° C.
 14. The processaccording to claim 8, wherein the diol and diester are used in a diol todiester molar ratio of 2.0-2.5.